The invention relates to an arrangement for mounting a shrouded pivotable propfan blade at a rotor, in which the propfan blade is fastened at a blade carrier and this blade carrier, by means of a roller bearing, is disposed in the rotor so that it can be adjustably pivoted around an axis which is radial with respect to the engine.
This type of an arrangement is known from German Published Unexamined patent application (DE-OS) No. 23 33 274, in which the propfan blade must be removed radially toward the outside.
From German Patent (DE-PS) No. 26 22 235, an arrangement is known for the swivelling of propfan blades of a turbo engine, in which, in each case, one shaft of a propfan blade is rotatably disposed in a rotor. At the shaft, a toothed wheel is fastened, which is arranged radially on the inside and engages with toothed rings disposed in the rotor for the purpose of swivelling the propfan blade.
These arrangements have the disadvantage that, if one blade is damaged, their removal is very costly. Thus, in the case of the latter, the toothed wheel located on the inside must be removed first before the blade can be pulled off radially toward the outside. Particularly, in propfan engines having a shroud radially outside the propfan blades, an opening in the shroud must be provided for this purpose. This requires higher mounting expenditures and increases the risk of damage to the shroud.
Starting from these conditions, it is an object of the invention to provide a mounting for a pivotable propfan blade which ensures a simple removal or exchange of the propfan blade also when a shroud is present. In particular, no intervention is to be required for this purpose on the inside of the rotor or in the swivelling mechanism.
This object is achieved in accordance with certain preferred embodiments of the invention by providing an arrangement for mounting a shrouded pivotable propfan blade at a rotor, in which the propfan blade is fastened at a blade carrier and this blade carrier, by means of a roller bearing, is disposed in the rotor so that it can be pivoted around an axis which is radial with respect to the engine, characterized that the propfan blade is held in a dovetail mounting in the blade carrier and, by means of a first securing device is fixed with respect to axial movements of the propfan blade and the blade carrier is secured by means of a second securing device accessible from the outside with respect to radial movements.
This object is achieved according to certain other preferred embodiments of the invention by providing an arrangement for mounting a shrouded pivotable propfan blade at a rotor, in which the propfan blade is fastened at a blade carrier and this blade carrier, by means of a roller bearing, is disposed in the rotor so that it can be pivoted around an axis which is radial with respect to the engine, characterized that the propfan blade has a disk-shaped blade base which, by means of a divided clamping ring is releasably fastened in the fitted disk-shaped upper part of the blade carrier and is secured by means of a securing device 8 which is accessible from the outside with respect to radial movements.
As a result of the arrangements of the present invention it can be advantageously achieved that a propfan blade, which is to be exchanged, must not be removed radially toward the outside, and thus no changes are required at the shroud. The removal of the propfan blade advantageously takes place by the fact that, after the removal of the first safety device, the blade can be removed axially out of the dovetail guide and, if necessary, the blade carrier can then, after the removal of the second safety device, be pulled out radially.
A removal of the profan blade or of the blade carrier or its bearing is possible without any intervention in the blade adjusting mechanism and the pertaining hydraulic system. As a result, a significant shortening and simplification of the repair process of the blade or the blade bearing can be achieved.
In an advantageous further development of the invention, the blade carrier is connected by means of a toothing with the pivoted adjusting lever in a non-rotatable manner. This permits a space-saving releasable connection which can be disengaged in a simple way. The toothing may be constructed either as a simple radial toothing or a wedge-type toothing.
Another advantageous development of certain preferred embodiments of the invention provides that a sleeve-type intermediate member is connected with the blade carrier by way of fastening, i.e., the fixing of the inner ring of the bearing by means of a thread, and has a toothing at its inner surface. As a result, a favorable fixing of the ring bearing can be advantageously combined with the possibility of a simple radial removal of the blade carrier.
In addition, it is provided in certain preferred embodiments that a tensioning nut, which is accessible from the outside while clamping in an outer ring of the bearing by means of a thread, is connected with the rotor. This permits a simple detachment of the blade carrier without any interventions into the pivot bearing or the interior of the rotor.
The blade carrier is preferably disposed by means of a double-row tapered roller bearing, whereby a favorable absorption can be achieved of the stress which occurs during the operation.
The dovetail mounting is preferably sloped with respect to the rotor axis. As a result, when a propfan blade is removed, an enlargement of the tip gap can be achieved which reduces the danger of damage to the blade tip or provided grazing coatings in the shroud.
A further development of the invention provides that one or several securing plates are provided for the axial securing of the propfan blades, these securing plates being fitted radially from the inside, into transverse grooves of the blade carrier and a dovetail-type constructed blade base, and being secured by means of a securing wedge which is slid axially under the blade base. As a result, a simple releasable axial fixing of the propfan blade can be achieved which is also low in weight.
In an advantageous further development of preferred embodiments, the dovetail mounting is constructed to be arcuate, ensuring a favorable fit with respect to the profile shape of the propfan blade.
According to an alternative solution of the problems on which the invention is based, the propfan blade is mounted at the blade carrier by means of clamping-ring segments. This permits a simple mounting and demounting of the propfan blade. Preferably, the clamping ring, which has a U-shaped cross-section, consists of two half-rings, which are fitted together under tension by means of connecting flanges. It is also contemplated to separate the clamping ring only at one point, so that the demounting takes place by the elastic bending-open of the clamping ring.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.